1. Field of the Invention
The invention relates to an image reading apparatus.
2. Related Background Art
In case of reading an image on an original by a copying apparatus, a facsimile apparatus, or an image reading apparatus such as an image scanner or the like, there is an apparatus having a function to variably magnify (zoom, namely, enlarge or reduce) a size of image to be read. In case of zooming an image by such an image reading apparatus, such a zoom processing is accomplished by changing a reading main scanning speed at which an image reading unit for optically reading an original is relatively moved for the original.
However, in order to read the original image at a low resolution by using an image scanner having a high reading resolution, it is necessary to scan an optical system at a very high speed for the original. To move the optical system at a high speed as mentioned above, a long approach run distance is needed, resulting in an enlargement in size of the apparatus. When a motor is operated at a high speed, since the vibration increases, it becomes a factor of deterioration of an image quality such as fluctuation of the image or the like. Further, a high speed and expensive driving motor is also necessary.